1. Field of the Invention
The present invention relates to a flat fluorescent lamp and optical fixing device. More particularly, the present invention relates to a flat fluorescent lamp and optical fixing device which can emit light at a sufficient amount even upon applying low voltage.
2. Description Related to the Prior Art
In FIG. 5, a conventional flat fluorescent lamp is depicted, and includes a pair of glass substrates 2 and 3, which a spacer 4 keeps at a small distance in parallelism. The glass substrate 2 is coated with a transparent planar electrode layer 2a, a transparent dielectric layer 2b and a fluorescent layer 2c overlaid on one another. The glass substrate 3 is coated with an opaque planar electrode layer 3a, a transparent dielectric layer 3b and a fluorescent layer 3c overlaid on one another. A discharge space 5 is filled with rare gas or mixture of rare gas and mercury vapor sealed therein by the glass substrates 2 and 3 and the spacer 4.
In the flat fluorescent lamp, the transparent dielectric layers 2b and 3b of glass or the like lie between the transparent and opaque planar electrode layers 2a and 3a. When a lamp drive device 6 causes the flat fluorescent lamp to illuminate, considerably high voltage must be applied by the lamp drive device 6 in comparison with voltage to be applied to a conventional light source. To lower the required voltage, it is possible to set high the degree of vacuum by lowering pressure of the sealed gas. However, the higher degree of vacuum raises the manufacturing cost.
JP-A 6-089653 discloses a flat fluorescent lamp in which plural projections are formed on a surface of electrodes. Corners of the projections cause electric field strength to be high, so as to enable driving at a low voltage. However, this type in which local highness in the electric field strength occurs by means of the projections has a shortcoming in that no projections can be formed on a transparent planar electrode layer on an output side of light.
In view of the foregoing problems, an object of the present invention is to provide a flat fluorescent lamp and optical fixing device which has a simple structure and can emit light at a sufficient amount even upon applying low voltage.
In order to achieve the above and other objects and advantages of this invention, a flat fluorescent lamp has a vessel or housing including first and second substrates opposed to each other at a small distance, and having discharge gas enclosed therein. A first planar electrode being transparent is disposed on an inner surface of the first substrate. A second planar electrode is disposed on an inner surface of the second substrate, for electrical discharge in cooperation with the first planar electrode. First and second dielectric layers are disposed on respectively the inner surfaces of the first and second substrates to cover the first and second planar electrodes. First and second fluorescent layers are overlaid on respectively inner surfaces of the first and second dielectric layers, for emitting electromagnetic rays in response to the electrical discharge between the first and second planar electrodes. At least one protruding pattern is formed with the inner surface of the first and/or second dielectric layers.
The protruding pattern includes plural projections.
The electromagnetic rays are ultraviolet rays or near ultraviolet rays adapted for fixing thermosensitive recording material.
The plural projections are arranged in a matrix manner.
The protruding pattern is formed with the inner surface of the second dielectric layer, and the first substrate emits the electromagnetic rays externally.
In a preferred embodiment, the at least one protruding pattern is first and second protruding patterns formed with respectively the inner surfaces of the first and second dielectric layers.
The first protruding pattern includes a first group of plural projections, the second protruding pattern includes a second group of plural projections, and the plural projections in the second group are offset from the plural projections in the first group.
In another preferred embodiment, the plural projections are arranged in at least first and second projection trains, each of the at least first and second projection trains includes plural projections arranged in a predetermined direction, and projections in the second projection train are disposed alternately with projections in the first projection train with reference to the predetermined direction.
The plural projections have a substantially hemispherical shape.
The plural projections have a height of 1-4 mm and a diameter of 0.5-2.0 mm, and are arranged at a pitch of 2-8 mm.
The first planar electrode is formed from indium tin oxide, the second planar electrode is formed from aluminum, and the first and second dielectric layers are formed from silicon dioxide.
The protruding pattern is formed by photolithography and etching.
In another aspect of the invention, an optical fixing device applies electromagnetic rays to thermosensitive recording material for fixation. The optical fixing device includes a vessel or housing, including first and second substrates opposed to each other at a small distance, and having discharge gas enclosed therein. A first planar electrode being transparent is disposed on an inner surface of the first substrate. A second planar electrode is disposed on an inner surface of the second substrate, for electrical discharge in cooperation with the first planar electrode. First and second dielectric layers are disposed on respectively the inner surfaces of the first and second substrates to cover the first and second planar electrodes. First and second fluorescent layers are overlaid on respectively inner surfaces of the first and second dielectric layers, for emitting the electromagnetic rays in response to the electrical discharge between the first and second planar electrodes. At least one protruding pattern is formed with the inner surface of the first and/or second dielectric layers.